The proposed research focuses on the development of a DNP-NMR system for Dynamic Nuclear Polarization (DNP) enhanced solid-state NMR spectroscopy at 400 MHz. High-resolution structures are essential to the understanding of the complex functions of bio-macromolecules and NMR spectroscopy is a major source for such information. However, the method suffers from an inherently low sensitivity and long acquisition times are required to achieve sufficient data quality. DNP, a method in which the high, thermal electron polarization is transferred to surrounding nuclei by THz irradiation of the sample, can boost the NMR sensitivity by two or three orders of magnitude. With DNP, experiments that typically require days or weeks of signal averaging can be performed in minutes or hours. It enables researchers to do experiments that are otherwise impossible to perform, such as high-precision distance measurements or recording 2D 13C-13C correlation spectra of unlabeled molecules in just hours. In this proposal we present a novel 400 MHz DNP system based on a 263 GHz gyrotron source that is integrated into the NMR magnet. Our product does not require an additional, expensive superconducting magnet. This is possible, because current (wide-bore) NMR magnets provide sufficient space right above the probe to integrate and operate the gyrotron source. This innovative gyrotron tube is specifically designed for DNP applications, provides sufficient power and has adequate frequency tuning bandwidth to eliminate the superconducting sweep coil that is necessary in other DNP systems. The presented innovations result in cost savings of >$ 0.8 million per unit and will make DNP a much more affordable method. During Phase I we will perform the mechanical and electrical design of the 263 GHz integrated THz source and select a cavity trim coil magnet assembly based on its NMR performance. During Phase II the gyrotron source will be fabricated and the complete DNP system including the low-temperature NMR probe will be integrated in the 400 MHz NMR magnet. As a result of this project, we expect a complete 400 MHz DNP system based on Bridge12's integrated gyrotron source and we expect signal enhancements of >100 in routine measurements. Although the product is initially targeted towards an academic market we expect that it will lay the foundation for a much broader acceptance of the technology in academia and industry and will bring the benefits of DNP to a much broader scientific audience.